Fix build against xorg-server >= 1.20.

Patch taken from upstream:
https://cgit.freedesktop.org/xorg/driver/xf86-video-savage/commit/?id=0ece556daa8a88771b669d8104396abd9166d2d0

diff --git a/src/savage_driver.c b/src/savage_driver.c
index 58a294d..3cda923 100644
--- a/src/savage_driver.c
+++ b/src/savage_driver.c
@@ -2034,8 +2034,6 @@ static Bool SavagePreInit(ScrnInfoPtr pScrn, int flags)
     xf86DrvMsg(pScrn->scrnIndex, X_PROBED, "Detected current MCLK value of %1.3f MHz\n",
 	       mclk / 1000.0);
 
-    pScrn->maxHValue = 2048 << 3;	/* 11 bits of h_total 8-pixel units */
-    pScrn->maxVValue = 2048;		/* 11 bits of v_total */
     pScrn->virtualX = pScrn->display->virtualX;
     pScrn->virtualY = pScrn->display->virtualY;
 
@@ -3637,6 +3635,14 @@ static ModeStatus SavageValidMode(SCRN_ARG_TYPE arg, DisplayModePtr pMode,
        (pMode->VDisplay > psav->PanelY)))
 	    return MODE_PANEL;
 
+    /* 11 bits of h_total 8-pixel units */
+    if (pMode->HTotal > (2048 << 3))
+	return MODE_BAD_HVALUE;
+
+    /* 11 bits of v_total */
+    if (pMode->VTotal > 2048)
+	return MODE_BAD_VVALUE;
+
     if (psav->UseBIOS) {
 	refresh = SavageGetRefresh(pMode);
         return (SavageMatchBiosMode(pScrn,pMode->HDisplay,
><a class='active' href='/guix/log/gnu/system/examples/docker-image.tmpl?showmsg=1'>log</a><a href='/guix/tree/gnu/system/examples/docker-image.tmpl?id=a2e661e95f8ab2fcb7741198234395b367a794c1'>tree</a><a href='/guix/commit/gnu/system/examples/docker-image.tmpl?id=a2e661e95f8ab2fcb7741198234395b367a794c1'>commit</a><a href='/guix/diff/gnu/system/examples/docker-image.tmpl?id=a2e661e95f8ab2fcb7741198234395b367a794c1'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/system/examples/docker-image.tmpl'>
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<div class='path'>path: <a href='/guix/log/?id=a2e661e95f8ab2fcb7741198234395b367a794c1&amp;showmsg=1'>root</a>/<a href='/guix/log/gnu?id=a2e661e95f8ab2fcb7741198234395b367a794c1&amp;showmsg=1'>gnu</a>/<a href='/guix/log/gnu/system?id=a2e661e95f8ab2fcb7741198234395b367a794c1&amp;showmsg=1'>system</a>/<a href='/guix/log/gnu/system/examples?id=a2e661e95f8ab2fcb7741198234395b367a794c1&amp;showmsg=1'>examples</a>/<a href='/guix/log/gnu/system/examples/docker-image.tmpl?id=a2e661e95f8ab2fcb7741198234395b367a794c1&amp;showmsg=1'>docker-image.tmpl</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/system/examples/docker-image.tmpl?id=a2e661e95f8ab2fcb7741198234395b367a794c1'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2019-03-25 23:37:06 +0100'>2019-03-25</span></td><td class='logsubject'><a href='/guix/commit/gnu/system/examples/docker-image.tmpl?id=cf848cc0a17a3a58d600116896f6e7abfb0440d4'>accounts: Add default value for the 'home-directory' field of &lt;user-account&gt;.</a></td><td>Ludovic Courtès</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/system/accounts.scm (&lt;user-account&gt;)[home-directory]: Mark as
thunked and add a default value.
(default-home-directory): New procedure.
* doc/guix.texi (User Accounts): Remove 'home-directory' from example.
* gnu/system/examples/bare-bones.tmpl: Likewise.
* gnu/system/examples/beaglebone-black.tmpl: Likewise.
* gnu/system/examples/desktop.tmpl: Likewise.
* gnu/system/examples/docker-image.tmpl: Likewise.
* gnu/system/examples/lightweight-desktop.tmpl: Likewise.
* gnu/system/install.scm (installation-os): Likewise.
* gnu/tests.scm (%simple-os): Likewise.
* gnu/tests/install.scm (%minimal-os, %minimal-os-on-vda):
(%separate-home-os, %encrypted-root-os, %btrfs-root-os): Likewise.
* tests/accounts.scm ("allocate-passwd")
("allocate-passwd with previous state"): Likewise.


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